This article describes the functions with which speakers of Medellín, Colombia, use the o sea discourse marker and its frequency of use. Regarding the methodology, 101 interviews were taken from the PRESEEA-Medellín corpus and they were classified according to the variables of age, gender, educational level and social class. The study concludes that speakers of Medellín use o sea primarily to reformulate the speech, but that they also use it with other less regulated functions. Likewise, it is observed that social variables significantly affect the linguistic variation of the marker.